The present invention generally relates to an oil filter-pump system for circulating oil through an electric power device such as a transformer load tap changer. The invention is particularly directed to apparatus that is useful for preventing environmental contamination resulting from the escape of dielectric insulation oil.
In the operation of certain electric power devices, such as transformers and the like, water droplets and graphite particles are inevitably entrained within the circulating oil used to cool such power devices. Oil circulation is necessary to reduce the temperatures that would otherwise be present. A standard practice is to connect the compartment in which the transformer load tap changer or the like is contained, and in which the cooling oil is present, to adjacently located pump and filter units by means of plumbing conduits. Circulation around the conduit loop is achieved by a pump motor which is controlled by a timer or timers and filter pressure differential monitoring switches.
A circulating oil system known in the art is found in U.S. Pat. No. 5,691,706, assigned to Filmax, Inc. This patent discloses an oil circulating system for a transformer including a load tap changer compartment connected by suction and discharge conduits to an area outside the compartment in which a filter and pump are located. The particular invention described therein is drawn to the objective of reducing or preventing leakage of oil from the transformer by giving an alarm of such leakage.
Another system in the prior art is one designed hereto fore by applicants' assignee, involving a circulating oil filter system but one which is typically add-on, rather than integral as is the case with the present invention. That prior cat design can be appreciated by reference to assignee's brochure OFS-G-1195A, published by Waukesha Electric Systems, Waukesha, Wis. 53186-5940.
Also known in the prior art is U.S. Pat. No. 4,075,099 assigned to Continental Group, Inc. which discloses a container assembly wherein the oil required for the changing of oil of a unit, such as an internal combustion engine, may be packed in a readily disposable container and wherein the container has built into it the usual filter so that in a simple operation both the filter and the old oil which contains contaminants, may be removed as a unit, whereby any oil lost in the filtering process due to adherence to the filter is completely replaced.
Although it will be clear that certain advantageous features are found in the systems of the prior art, nevertheless, there is a serious lack .n such systems inasmuch as the circulating pumps in the systems are susceptible to leakage with consequent damage to the local area and to the environment in general.
Accordingly, it is the primary object of the present invention to reduce substantially the leakage which occurs in an oil circulation system of the type described, that is, one which is directed to reducing the high temperatures normally produced in the operation of power devices such as large transformers and the like.
A related object is to insure that the motor and pump combination operate efficaciously, that is, the motor driving the pump is so coupled to the pump as to be capable of operating with only some slight amount of misalignment, the tolerable amount being achieved by an adapter means.
Other related objects are to insure that the most contaminated oil is removed first so that the greatest efficiency is achieved in contaminant removal.
Another object is to prevent loss of oil in the event of a break in the pick-up or return tubes by providing anti-siphon holes in such tube.
Yet another object is to monitor completely the operation of the system by providing a pressure release device, and pressure switches which incorporate both high and low pressure contacts, whereby if the pressure is too low a pump problem is indicated or an oil level problem. On the other hand, if the pressure is too high it indicates a plugged filter or other resistance to flow.